1. Field of the Invention
The present invention relates to image-taking apparatuses which can distribute taken images over a network, such as a LAN, or the Internet.
2. Description of Related Art
In recent years, image-taking apparatuses referred to as “network cameras” which directly distribute image information over a LAN or the Internet are increasingly replacing cameras which save images (moving images or still images) that have been taken on recording media, such as tape or film. Such network cameras can be installed in a scenic spot or a busy street, or at an inaccessible location, and images of that place can be viewed live without actually going to that location.
Such network cameras are connected to a network, such as a LAN, and the taken images are displayed on the display monitors of personal computers connected to the network.
Moreover, over the network such network cameras can be caused to perform such camera operations as panning, tilting or zooming, and can be caused to take images of the typically desired direction or size on the network.
In current network cameras, there is a limit to the capacity of communication lines, and when moving images are taken at a rate of 30 frames per second, then the resolution is limited about to CIF level (352×288 pixels) However, the resolution of image-pickup devices, such as CCDs, is getting higher, and there are also video cameras on the market that have a function of taking still images with high resolution. These use image-pickup devices with many pixels, and take the images at NTSC level or PAL level when taking moving images, but use the pixels fully when taking still images, thus achieving high resolutions of the XGA level and higher.
Moreover, also future network cameras take video at the CIF level and film moving images at 30 frames per second, but for still images or at low frame levels of only one or two frames per second, they may take images at high resolutions of XGA level or higher (see Japanese Patent Application Laid-Open No. 2001-189932).
Different from images taken with ordinary video cameras or the like, the images taken with such network cameras are anonymous in the sense that the camera may be operated by an unspecified large number of people over the network, and it is unknown who takes which images. For this reason, it is necessary to respect the privacy of the people whose images are taken, to avoid image-taking with ill intent.
Moreover, the image-taking lenses used for video cameras or network cameras often have a very high magnifying power with a zoom ratio of ×10 to ×20, so that converting this to 35 mm film, it becomes possible to take images ranging from standard regions of about 40 mm to very far regions of maximally about 800 mm. With far regions with a focal length of 800 mm, the faces of people located far away can be magnified greatly, such that they can be pictured clearly. Therefore, it becomes even more necessary to respect the privacy of the pictured people.
For surveillance cameras, it has been suggested to take images while respecting privacy by masking a portion of the image, as has been proposed in Japanese Patent Application Laid-Open No. 2001-69494 (corresponding to European Patent Application Publication 1 081 955 A2).
However, the proposal of Japanese Patent Application Laid-Open No. 2001-69494 can be used only in the closed environment of a surveillance camera, and if the taken images can be viewed openly by an unspecified large number of people, as in the case of a network camera, then the masked portion becomes unsightly, compromising the appeal of the images.
Moreover, since moving images and still images are taken with the same image-pickup device and distributed to the network using the same line, there is a limit to the distribution of ordinary moving images if large data volumes of images, such as still images of high image quality, are distributed. Therefore, there is a need for avoiding the distribution of unnecessarily large data amounts of images that are out of focus or not properly exposed.